was possible, especially in a nonindustrial context, was that you had a very effective agricultural environment around fez within, say, 15 or 20 miles radius. but you also had very effective forms of nonhuman transport -- donkeys, camels, horses, mules -- that could bring in all of the kinds of supplies that the city needed. now, that's one reason why you had such high population densities. one of the effects of really high population densities, of course, is to create very dense urban markets, lots of consumers concentrated in small spaces. and this is one of the reasons why fez has such a high degree of urban specialization. keach: as in ancient ostia, almost everyone in fez is a full-time specialist. in the tanning industry alone, there are some 20 specialized activities required to process skins into leather. there are washers and hair removers, buyers and sellers, and transport specialists. there are even specialties within a specialty. there are people who handle the donkeys that bring skins into the market, while others handle the donkeys taking skins out. this is a hair removing factory